109P/Swift-Tuttle

Infobox Comet
name=109P/Swift-Tuttle


discoverer=Lewis Swift Horace Parnell Tuttle
discovery_date=July 16, 1862
designations=1737 N1; 1737 II; 1862 O1; 1862 III; 1992 S2; 1992 XXVIII
epoch=October 10, 1995 (JD 2450000.5)
semimajor=26.092 AU
perihelion=0.9595 AU
aphelion=51.225 AU
eccentricity=0.9632
period=133.28 a
inclination= 113.45°
last_p=December 11, 1992
next_p=July 12, 2126

Comet Swift-Tuttle (formally designated as 109P/Swift-Tuttle) was independently discovered by Lewis Swift on July 16, 1862 and by Horace Parnell Tuttle on July 19, 1862.

The comet made a return appearance in 1992, when it was rediscovered by Japanese astronomer Tsuruhiko Kiuchi.

It is the parent body of the Perseid meteor shower, perhaps the best known shower and also among the most reliable in performance.

The comet is on an orbit which will almost certainly eventually hit either the Earth or the Moon, though not within this millennium. [cite web|url=http://www.newscientist.com/article.ns?id=dn7449|title=Comet put on list of potential Earth impactors|last=Chandler|first=David L|date=2005-06-01|publisher=New Scientist|accessdate=2008-08-25] Upon its 1992 rediscovery, the comet's date of perihelion passage was off from the then-current prediction by 17 days. It was then noticed that, if its next perihelion passage (August 14, 2126) was also off by another 15 days, the comet would very likely strike the Earth or Moon. Since Swift-Tuttle is about the same size as the comet thought to have caused the Cretaceous–Tertiary extinction event, this was of some concern. However, study of earlier passages of the comet, dating as far back as 69 BC, led to a recalculation of its orbit - the new orbit's stability turned out to be greater than expected, making the threat disappear. [cite web|url=http://www.as.wvu.edu/~jel/skywatch/swfttle.html|title=on Swift-Tuttle's possible collision|last=Stephens|first=Sally|date=1993|publisher=Astronomical Society of the Pacific|accessdate=2008-08-25]

Notes

External links

* [http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=109P 109P/Swift-Tuttle] at NASA's Jet Propulsion Laboratory's Small-Body Database
* [http://apod.nasa.gov/apod/ap960219.html Periodic Comet Swift-Tuttle] from NASA's Astronomy Picture of the Day